Armco Galvanizers Isando and Randfontein: Why Hot-Dip Galvanisation?

 Armco Galvanizers Isando is one of the largest galvanising plants in South Africa. The location of the plant makes it possible to ship large construction, engineering, road building and mine-related galvanised products across the country.

With Armco Galvanizers at Isando and Randfontein meeting the quality management system requirements of BSI ISO 9001: 2015, clients have the assurance of ongoing improvements in quality, strict monitoring and adherence to international standards for quality related to production, product supply and services. The firm has quality plans in place for every operation to ensure consistency, meeting of client expectations, and quality throughout the processes and service delivery. Armco Galvanizers

Armco Galvanizers Isando and Armco Galvanizers Randfontein, both located in Gauteng, hold the Hot Dipped Galvanising SATAS mark, giving clients even more assurance of safe and durable products suitable for their particular applications.

In addition, Armco Galvanizers in Isando and Randfontein galvanise products according to the specification requirements of SANS 121 / ISO 1461, with certificates available to clients upon request.

More about the Armco Galvanizers Isando

The Isando plant has been in operation for almost four decades. With a proven track record of processes, large, completed projects and satisfied clients, Armco Superlite has set itself up as one of the leading galvanizers in the country.

The Isando plant has galvanisation baths that can handle structural steel in lengths of up to 13 metres by 1.45 metres wide and have the capacity to handle up to 2 000 tons of steel galvanisation per year.

More about Armco Galvanizers Randfontein

The second plant can handle in the vicinity of 800 tons of steel monthly. Unlike the Isando plant geared for heavy structural steel, the galvanizers at Randfontein have been designed for galvanisation of light and medium structural steel of lengths up to 6 metres by 1.45 metres wide.

More about hot-dip galvanisation

Also known as HDG (hot-dip galvanising), it entails the coating of steel by means of dipping the steel in a bath of hot molten zinc. Before the steel is dipped or immersed, it must be prepared.

How the surface preparation works

The steel is first placed on a rack that can be moved through special equipment or is hung and then cleaned. The first step is to degrease the surface to eliminate any areas where oil residue can affect the coating. This process also removes organic debris and dirt particles.

Once done, the steel is pickled. This is for the removal of iron oxide in addition to mill scale. The pickling process is followed by fluxing which entails the removal of left-over oxide and scale. With fluxing, the surface also receives a protective layer, which eliminates further iron oxide development before the steel is hot-dip galvanised. With the surface properly cleaned and prepared, the zinc can react and bond with the metal through the hot-dip process to ensure durable protection.


The next step at the Isando plant is the hot-dipping process. To ensure proper bonding takes place, the solution is heated to at least 443°C. The steel is placed in the bath at a specific angle. This makes it possible for air to be removed from the tubular types of steel, corners and any uneven parts on the surface. With the steel at an angle, the molten zinc can flow unhindered to cover the entire surface evenly.

The hot molten zinc reacts with the steel, leading to several zinc-iron bonded layers. A zinc-only layer forms on top of the underlying zinc-iron layers, giving the surface optimal protection.

Quality inspection

Once the steel has been hot-dip galvanised, it’s allowed to dry and an inspection follows. This entails a visual inspection to identify any areas where the zinc has not covered the steel. A thickness gauge technology is applied to measure thickness where relevant to confirm the layer thickness.

Why zinc is used by the galvanizers and why hot-dip galvanisation is beneficial

The zinc and the steel bond metallurgically for several layers between the underlying surface and the external surrounds. These layers also add cathodic protection to the underlying surface, which means the zinc sacrifices itself to protect the steel.

Because of the diffusion that occurs in the molten zinc bath and the angle at which coating takes place, the entire surface is covered, even the smallest of areas. In addition, a zinc patina forms on top, giving durable protection. With this, the surface is protected for a long time without additional regular coatings or maintenance required. With no additional maintenance needed, galvanised steel’s cost-of-ownership over the lifespan of the steel remains low.

Hot-dip galvanisation holds several benefits. For one, the steel is ready for use in harsh environments. With high corrosion resistance, it can be used for the construction of culverts, guardrails, roofs and even buildings. Corrosion compromises the steel’s integrity as weak areas develop, which can lead to structural failure.

To ensure the steel used in construction projects can last for years and stay strong, it’s essential to ensure adequate protection. This is achieved with hot-dip galvanisation as the zinc is not just a protective coat. The first few layers are a metallurgical bond of zinc and iron. With a conventional protective coat, the coat lies on top of the surface. If the protective coat is damaged, the underlying steel surface is exposed and starts to corrode. With the bonding of zinc and iron, the zinc yields itself, thereby preventing the steel from corroding even if the upper zinc-only layer is scratched, and the underlying zinc-iron layers are exposed.

Hot dipping ensures that every part of the steel is covered and protected, leaving no part exposed. In addition, it helps to create an attractive surface, free from blemishes. Furthermore, the galvanised steel can be recycled and used in other projects should a structure no longer be required.

The longevity of structures is important to help minimise development- and economic-based footprints on the environment. Hot-dipped galvanised steel lasts many years, thereby reducing the need for regular replacement of structures.

Why galvanise products, using the services offered at Armco Galvanizers Isando and Randfontein?

As mentioned earlier, these plants have been operational for many years. The firm has a proven track record of compliance with quality standards and with the required equipment to ensure consistency clients have the assurance of quality. Armco Superlite also produces a range of galvanised steel products that are used for road safety applications and construction purposes. The products have stood the test of time. The Armco Galvanizers Isando and Randfontein plants are local, ensuring faster delivery of products than would be the case with imports. Reach out for more information and quotes on galvanisation.